By the beginning of the war the Soviet Army was made a lot of rockets: 82 mm shrapnel shells of M-8; 132-mm high-explosive rockets M-13 - it's the ones that mass placed on the first "Katyusha"; 132-mm high-explosive projectile M-20; 300-mm high-explosive rockets M-30, M-31 and M-31 of the Criminal Code; 280 mm turbojet explosive projectile M-28. Will focus in more detail on the M-20 and M-30, because they can be considered as the beginning of a heavy rocket artillery.
M-13 on the "Katyusha" course were good, sudden massive shelling caused in the ranks of the Germans terrible fear, and so on, but for the full-fledged offensive operations they are not very fit - small enough damage. And it was necessary to destroy as heavy equipment and ukrepsooruzheniya. Therefore, by the middle of '42 were put into service the shells of M-20 warhead which was almost 3. 5 times more powerful than the M-13, and very soon and the new M-30 missiles - almost 6 times more powerful.
M-20 successfully tightened the "Katyusha", but because of the slightly larger they had to run only one row instead of two. But under the M-30 guides are not fit (running forward to say that they still prikolhozili, but only in '44), so start them were made primitive launchers machines with adjustable angle.
Shells on the machine fit directly into the factory wooden packaging containers, first by 4 per pack, then wholesale at 8. incinerate the whole thing in one fell swoop using conventional electric demining machines, and it was possible to simultaneously connect multiple machines. The simultaneous launch of guaranteed addition of shock pulses in the landing area, which was more effective than individual starts.
But because of the reluctance of the eternal end users to read manuals, or rather, manuals sharply disagreed on cigarettes and still smoke each ordinary (here's a pun) on the battlefields often happened next. In preparation for shooting forget to remove the spacers that held the projectile inside the frame during transport. And of course it all started from a place with a wooden box, and sometimes with the machine. And the size of the design was about 1, 5 to 2 meters, and subsequently led to conversations in the ranks of the Germans that the Russian and shoot quite ofigeli already sheds.